Answer:
D (Presumably)
16 by 3
Explanation:
The perimeter of a rectangle is the two lengths added with the two widths. In a formula, this is:

Where l is the length and w is the width.
We are told the length is 13 units longer than the width. In other words:

We also already know that the perimeter is 38 units. So, let's substitute P for 38 and l for (w+13) to solve for w:

Distribute:

Combine like terms:

Subtract 26 from both sides:

Divide both sides by 4:

Thus, the width is 3 units.
Since the length is 13 units longer than the width, the length is 16 units.